Accent problem when searching for users

[Clementine46]

When looking for a user in the "add users" modal you need to take into account the accents in someone's name, otherwise the user won't be found.

For example, the user "Céline Pariel" can only be found if you type "cé" and not "ce". This is an unexpected behavior since "é" is a variation of the letter "e" and it can be problematic for people who aren't used to accents.

Both "ce" and "cé" should give the same results when searching for a user.

[LivOriona]

Same issue as #472